U.S. patent number 8,506,812 [Application Number 13/555,668] was granted by the patent office on 2013-08-13 for method, equipment and specific drawer for membrane separation utilizing concentration polarization.
This patent grant is currently assigned to Institute of Process Engineering, Chinese Academy of Sciences. The grantee listed for this patent is Xiangrong Chen, Zhanfeng Cui, Xiaoguang Jiao, Guanghui Ma, Fei Shen, Zhiguo Su, Yinhua Wan. Invention is credited to Xiangrong Chen, Zhanfeng Cui, Xiaoguang Jiao, Guanghui Ma, Fei Shen, Zhiguo Su, Yinhua Wan.
United States Patent |
8,506,812 |
Wan , et al. |
August 13, 2013 |
Method, equipment and specific drawer for membrane separation
utilizing concentration polarization
Abstract
The present invention relates to a membrane separation method
and a relevant equipment, in particular to a method and an
equipment for membrane separation utilizing concentration
polarization during membrane filtration process, especially, to a
concentration process and equipment and a drawer special for
drawing a concentration polarization layer. The direct removal of
the concentration polarization layer from membrane surface not only
decreases the adverse influence of concentration polarization on
membrane separation but also obtains concentrated retention
components, thereby significantly improving the ability to maintain
membrane flux, solving the twinborn problems concerning
concentration polarization and membrane fouling during the membrane
separation process, and achieving a high-efficiency concentration
for retention components. The method and equipment of the present
invention can be widely applied in various membrane techniques, in
particular in a membrane separation process for concentrating
biomacromolecule and organic micromolecule products such as sugars,
organic acids and polypeptides etc.
Inventors: |
Wan; Yinhua (Beijing,
CN), Chen; Xiangrong (Beijing, CN), Su;
Zhiguo (Beijing, CN), Ma; Guanghui (Beijing,
CN), Jiao; Xiaoguang (Beijing, CN), Shen;
Fei (Beijing, CN), Cui; Zhanfeng (Oxford,
GB) |
Applicant: |
Name |
City |
State |
Country |
Type |
Wan; Yinhua
Chen; Xiangrong
Su; Zhiguo
Ma; Guanghui
Jiao; Xiaoguang
Shen; Fei
Cui; Zhanfeng |
Beijing
Beijing
Beijing
Beijing
Beijing
Beijing
Oxford |
N/A
N/A
N/A
N/A
N/A
N/A
N/A |
CN
CN
CN
CN
CN
CN
GB |
|
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Assignee: |
Institute of Process Engineering,
Chinese Academy of Sciences (Beijing, CN)
|
Family
ID: |
39788053 |
Appl.
No.: |
13/555,668 |
Filed: |
July 23, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20120285889 A1 |
Nov 15, 2012 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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12443797 |
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8252184 |
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PCT/CN2008/070420 |
Mar 5, 2008 |
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Foreign Application Priority Data
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Mar 23, 2007 [CN] |
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2007 1 0064721 |
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Current U.S.
Class: |
210/637;
210/416.1; 210/106; 210/159; 210/327; 210/396; 210/158; 210/636;
210/791; 210/670; 210/167.14; 210/321.69; 210/167.09 |
Current CPC
Class: |
B01D
61/145 (20130101); B01D 63/082 (20130101); B01D
61/147 (20130101); B01D 65/08 (20130101); B01D
2321/26 (20130101) |
Current International
Class: |
B01D
33/44 (20060101); B01D 29/075 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2635198 |
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Aug 2004 |
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CN |
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1674974 |
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Sep 2005 |
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CN |
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1724411 |
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Jan 2006 |
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CN |
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2761253 |
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Mar 2006 |
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CN |
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2761254 |
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Mar 2006 |
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CN |
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07185268 |
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Jul 1995 |
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JP |
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2000051670 |
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Feb 2000 |
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JP |
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WO-9910088 |
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Mar 1999 |
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WO |
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WO-2004080510 |
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Sep 2004 |
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WO |
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Other References
International Search Report regarding International Application No.
PCT/CN2008/070420 dated Jun. 12, 2008. cited by applicant .
William Eykamp and Jonathan Steen. Chapter 18: Ultrafiltration and
Reverse Osmosis. Handbook of Separation Process Technology. Edited
by Ronald W. Rousseau, Georgia Institute of Technology. 1987. cited
by applicant .
Notice of Allowance regarding U.S. Appl. No. 12/443,797, mailed
Apr. 24, 2012. cited by applicant .
Final Office Action regarding U.S. Appl. No. 12/443,797, mailed
Jan. 26, 2011. cited by applicant .
Non-Final Office Action regarding U.S. Appl. No. 12/443,797, mailed
Oct. 13, 2010. cited by applicant .
Non-Final Office Action regarding U.S. Appl. No. 12/443,797, mailed
Jun. 4, 2010. cited by applicant .
Restriction/Election Requirement regarding U.S. Appl. No.
12/443,797, mailed Mar. 24, 2010. cited by applicant .
Jiao Xiaoguang et al. "Ultrafiltration and concentration of
bio-macromolecule solution using concentration polarization."
Thesis summary of 3rd Chinese National Chemical and Biochemical
Engineering Annual Meeting. Published Dec. 31, 2006. p. 591. cited
by applicant .
B. Sen. Gupta et al. "Effects of colloidal fouling and gas sparging
on microfiltration of yeast suspension." Published Aug. 11, 2005.
cited by applicant .
Extended European Search Report regarding Application No.
08715156.9-2113 / 2092974, dated May 2, 2012. cited by applicant
.
S.S. Sablani et al. "Concentration polarization in ultrafiltration
and reverse osmosis: a critical review." Desalination 141 (2001).
pp. 269-289. Dec. 30, 2001. cited by applicant.
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Primary Examiner: Menon; Krishnan S
Assistant Examiner: Gionta; Allison M
Attorney, Agent or Firm: Harness, Dickey & Pierce,
P.L.C.
Claims
What is claimed is:
1. A membrane separation method, comprising: a) loading a fluid
containing a retention component and a permeation component at a
separation side of a separation membrane; b) exerting a driving
force on said fluid to allow at least part of said permeation
component to pass through said separation membrane and arrive at a
permeation side of the separation membrane, thereby forming a
retention component-enriched concentration polarization layer at
said separation side of said separation membrane; and c) removing
at least part of said concentration polarization layer from said
separation side by means of a drawer to obtain concentrated
retention components, wherein said drawer comprises a hollow pipe
structure having at least one opening, a section with an opening of
said hollow pipe structure is over a feed-side surface of said
separation membrane, said opening configured to face said feed-side
surface of said separation membrane and be located inside said
concentration polarization layer at the separation side of said
separation membrane such that at least part of said concentration
polarization layer passes through said opening into said hollow
pipe structure, and is removed from said separation membrane along
a direction essentially normal to the separation membrane.
2. The membrane separation method according to claim 1, wherein
said driving force is produced by a pressure differential, a
concentration differential, a potential differential or a
temperature differential.
3. The membrane separation method according to claim 2, wherein
said driving force produced by said pressure differential generates
a transmembrane pressure ranging from 0.005 MPa to 10 MPa.
4. The membrane separation method according to claim 1, wherein all
or part of the steps of said membrane separation method are
performed continuously, semi-continuously or in an intermittent
manner.
5. The membrane separation method according to claim 3, wherein
said concentration polarization layer is continuously removed by a
drawing operation.
6. The membrane separation method according to claim 3, wherein
said concentration polarization layer is removed by an intermittent
drawing operation manner, wherein when any of said transmembrane
pressure, a permeation flux or a thickness of the concentration
polarization layer reach a first predetermined value, said drawing
of said concentration polarization layer is initiated; and when any
of said transmembrane pressure, said permeation flux or said
thickness of said concentration polarization layer reach a second
predetermined value, said drawing operation stops.
7. The membrane separation method according to claim 1, wherein
said membrane separation comprises a membrane concentration, a
membrane filtration, a membrane distillation, a membrane extraction
or a membrane absorption.
8. The membrane separation method according to claim 2, wherein
said driving force by said pressure differential generates a
transmembrane pressure ranging from 0.01 MPa to 4 MPa.
9. The membrane separation method according to claim 6, wherein
said steps of initiating and stopping said drawing operation are
performed repeatedly.
Description
TECHNICAL FIELD
The present invention relates to a method and equipment for
membrane separation, in particular to a method and equipment as
well as a specific drawer for the separation utilizing
concentration polarization during membrane separation
processes.
BACKGROUND ART
Membrane separation refers to a method for separation,
concentration and purification of a raw material by using a
selective permeation membrane, in which the components of the raw
material at the side of raw material selectively permeate the
membrane when there exists a certain driving force (such as
pressure difference, concentration difference, potential difference
or temperature difference etc.). Different membranes and driving
forces are employed in different membrane separation processes. At
present, the membrane separation processes that have been
industrially used include microfiltration (MF), ultrafiltration
(UF), reverse osmosis (RO), dialysis (D), electrodialysis (ED), gas
separation (GS), pervaporation (PV) and emulsion liquid membrane
(ELM) etc. In addition, there are many novel membrane separation
processes under development, such as membrane extraction, membrane
distillation, bipolar membrane electrodialysis, membrane split
phase, membrane absorption, membrane reaction, membrane control
release, membrane biosensor, etc.
As compared to traditional separation methods, the membrane
separation technique has the following advantages: (1) High
efficiency: since a membrane is selective, some substances can pass
through it selectively, while other substances are retained by it.
Effective separation, purification and concentration can be
performed by selecting and utilizing a suitable membrane; (2)
Energy saving: most of membrane separation processes are operated
at a room temperature without phase transition of a separated
substance, so membrane separation technique is an unit operation
with low energy consumption and low cost; (3) Membrane separation
processes are simple, easy to be operated and controlled; and (4)
There is no environmental pollution during the membrane separation
processes.
Therefore, the membrane separation technique has been developed
rapidly in recent years, widely applied in petrochemical industry,
biological pharmaceutical industry, medical and sanitation fields,
metallurgy industry, electronics, energy field, light industry,
textile industry, food industry, environmental protection industry,
aerospace industry, maritime transport industry and daily life
field, and becomes one of the most important means in separation
science nowadays.
However, concentration polarization phenomenon generally existing
in membrane separation processes is one of main factors affecting
membrane flux and causing membrane fouling. Concentration
polarization phenomenon refers to a phenomenon that a separation
membrane selectively allows some components in a raw material to be
separated to pass through but other components to be retained,
which results in the enriching of the retention components near to
the membrane surface of separation side to form a concentration
gradient from the membrane surface to the raw material bulk phase,
thereby causing a diffusion of the retained components from the
membrane surface to the raw material bulk phase and a decrease of
membrane flux. For example, during membrane separation of a
solution, the treated solution convectively flows to membrane
surface, and the retained solute accumulates near to the membrane
surface, so that the concentration of solute on membrane surface is
higher than that in the solution bulk phase, and a concentration
gradient from the membrane surface to solution bulk phase is
formed, which causes a diffusion of the retained components from
the membrane surface to the raw material bulk phase and a decrease
of flux. The above phenomenon is called concentration
polarization.
Since concentration polarization not only causes the decrease in
membrane flux but also aggravates membrane fouling due to the
enriching of retention components on membrane surface,
concentration polarization is a problem generally to be solved
during membrane separation processes. For example, the substances
with a high concentration on membrane surface may be removed by
tangential flow based on the optimization of membrane module design
and of operation conditions to reduce concentration polarization on
membrane surface and to maintain membrane flux. However, the
methods and equipments for reducing concentration polarization and
membrane fouling to maintain membrane flux still need to be
developed.
CONTENTS OF THE INVENTION
On the one hand, the present invention provides a membrane
separation method, which comprises: a) loading a fluid containing
retention components and permeation components at a separation side
of a separation membrane; b) exerting a driving force on the fluid
to allow at least part of the permeation components to pass through
the separation membrane and reach a permeation side of the
separation membrane, thereby a retention components-enriched
concentration polarization layer is formed at the separation side
of the separation membrane; and c) removing at least part of the
concentration polarization layer from the separation side.
In some embodiments of the membrane separation method according to
the present invention, the fluid is a fluid containing components
capable of forming a concentration polarization layer at the
separation side of the separation membrane, for examples, said
fluid can be a solution, a liquid-solid suspensoid, a liquid-liquid
suspensoid, a sol, a gas mixture, a gas-solid suspensoid, a
gas-liquid suspensoid, or an aerosol.
In some embodiments of the membrane separation method of the
present invention, said retention components refer to any
components in the fluid, which can be retained at least partially
by the separation membrane, such as one or more solute molecules or
ions, solid particles and liquid droplets etc., in particular
organic or inorganic solutes, more particularly biomacromolecule
such as proteins, nucleic acids and polysaccharides etc., and
biomicromolecule such amino acids, nucleotides and monosaccharides
etc. Said permeation components refer to any components in the
fluid, which can at least partially permeate the separation
membrane, such as one or more liquid solvents, carrier gases and
components different from the retention components, such as
molecules or ions, etc. In some embodiments, said retention
components may form a filter cake at the separation side, and/or
enter into and block membrane pores, and/or permeate the separation
membrane, in addition to the formation of a concentration
polarization layer.
In some embodiments of the membrane separation method of the
present invention, said separation membrane refers to any of
membranes that can be used for membrane separation, such as
nanofiltration membranes, ultrafiltration membranes and
microfiltration membranes, in particular nanofiltration,
ultrafiltration or microfiltration membranes made of celluloses,
poly(ether sulfone)s, polysulfones, polyolefins, polyamides,
polypiperazidines, metals, glasses or ceramics.
In some embodiments of the membrane separation method of the
present invention, said separation membrane may be present in any
suitable configuration, such as tabular, plate-and-frame, spiral,
tubular or hollow fiber.
In some embodiments of the membrane separation method of the
present invention, said separation membrane has a suitable
permeation flux, for example, ranging from 1.times.10.sup.-8 m/s to
1.times.10.sup.-4 m/s, preferably from 2.78.times.10.sup.-7 m/s to
1.39.times.10.sup.-4 m/s, more preferably from 1.84.times.10.sup.-6
m/s to 3.69.times.10.sup.-5 m/s.
In some embodiments of the membrane separation method of the
present invention, said driving force may be produced by any
suitable mode, such as pressure difference, concentration
difference, potential difference or temperature difference, in
particular pressure difference. For example, a positive pressure is
exerted at the separation side of a membrane or a negative pressure
is exerted at the permeation side of a membrane by a known means to
produce a pressure difference, wherein the positive pressure may be
produced at the separation side of a membrane using pump, positive
pressure fluid, gravity or centrifugal force etc., while the
negative pressure may be produced by a vacuum action or capillary
action at the permeation side of a membrane, and thus the
permeation components permeate the separation membrane from the
separation side to the permeation side under the pressure
difference to form a retention components-enriched concentration
polarization layer on the membrane surface of the separation
side.
In some embodiments of the membrane separation method of the
present invention, a transmembrane pressure generated by the
driving force produced by a pressure difference can be determined
in accordance with the requirements of application and actual
demands, for example, it ranges from 0.005 MPa to 10 MPa,
preferably from 0.01 MPa to 4 MPa.
In some embodiments of the membrane separation method of the
present invention, a step of removing permeation components from
the permeation side of the separation membrane is comprised
optionally. The step can be implemented by any known method
according to specific situations in said embodiments, for example,
the permeation components may be removed using a ductwork etc.
In some embodiments of the membrane separation method of the
present invention, the thickness of said concentration polarization
layer and the concentration of retention components therein can be
determined or adjusted based on the property of fluid and each
component therein, type of membrane module, kind and specification
of membrane, operation conditions including kind and magnitude of
driving force and fluid speed on the membrane surface according to
specific applications and requirements. For example, the thickness
of concentration polarization layer may be approximately predicted
by models (such as S. P. Agashiche, Calculation of concentration
polarisation in processes of ultrafiltration of non-Newtonian
fluids in tubular channel, Separation/Purification Technology 25
(2001) 523-533; S. K. Karode, A new unsteady-state model for
macromolecular ultrafiltration, Chemical Engineering Science 55
(2000) 1769-1773; S. Kim, E. M. V. Hoek, Modeling concentration
polarization in reverse osmosis processes, Desalination 186 (2005)
111-128; and Mohd. Z. Sulaiman et al., Prediction of dynamic
permeate flux during cross-flow ultrafiltration of polyethylene
glycol using concentration polarization-gel layer model, Journal of
Membrane Science 189 (2001) 151-165), and/or determined by
experiments (such as Z. Zhang et al., Use of capacitive
microsensors and ultrasonic time-domain reflectometry for in-situ
quantification of concentration polarization and membrane fouling
in pressure-driven membrane filtration, Sensors and Actuators B 117
(2006) 323-331; and J. C. Chen et al., In situ monitoring
techniques for concentration polarization and fouling phenomena in
membrane filtration, Advances in Colloid and Interface Science 107
(2004) 83-108 etc.). Hence, in some embodiments, the time, duration
and quantity for removing concentration polarization layer can be
determined according to a predicted, experimentally detected or
real-time detected thickness of the concentration polarization
layer and to specific application conditions and requirements.
In some embodiments of the membrane separation method of the
present invention, at least part of the concentration polarization
layer can be removed by any suitable method in the step c). For
example, the at least part of concentration polarization layer may
be removed by operations such as drawing, extracting or isolating
to make the removed at least part of concentration polarization
layer to be separated from said concentration polarization layer
and said fluid. In particular, a concentration polarization layer
is drawn or extracted using a ductwork; or a concentration
polarization layer is isolated from other parts of fluid using a
suitable container and then is extracted. In some embodiments,
drawing operation may be carried out using a pressure difference
between the concentration polarization layer and a drawer. The
operation of removing the at least part of concentration
polarization layer may be carried out at any place of the
concentration polarization layer, in particular, such operation is
carried out at a place close to the surface of separation membrane,
more particularly, such operation is carried out essentially on the
surface of separation membrane. Typically, after being separated
from said concentration polarization layer, the removed at least
part of concentration polarization layer does not go back to the
said fluid to avoid the remixing or back mixing between the removed
part of concentration polarization layer and the fluid, which may
be advantageous to applications such as membrane concentration.
However, in some applications, after being separated from said
concentration polarization layer, the removed part of concentration
polarization layer may still remix with the fluid, for example,
said remixing is conducted at a place other than those at which the
membrane separation is carried out. In some embodiments, the fluid
treated by the membrane separation method and/or the removed part
of concentration polarization layer may be optionally further
treated at a place same as or different from those at which
membrane separation is carried out.
In some embodiments of the membrane separation method of the
present invention, said concentration polarization layer is
separated from said separation membrane essentially along a normal
direction or a tangential direction or any direction between the
normal and tangential direction of the separation membrane.
In some embodiments of the membrane separation method of the
present invention, all or part of the steps of said membrane
separation are conducted continuously, semi-continuously or
intermittently. For example, the operation of removing at least
part of the concentration polarization layer may be carried out
continuously or intermittently to expediently remove from 0.1% to
99% of the concentration polarization layer continuously or
intermittently. For example, as for a continuous drawing operation,
when the transmembrane pressure or the permeation flux or the
thickness of concentration polarization layer reaches a
predetermined value, the concentration polarization layer may be
drawn continuously. As for a intermittent drawing operation, when
the transmembrane pressure or the permeation flux or the thickness
of concentration polarization layer reaches a first predetermined
value, the draw of the concentration polarization layer is
initiated; when the transmembrane pressure or the permeation flux
or the thickness of concentration polarization layer reaches a
second predetermined value, the drawing operation stops; and these
steps are repeated.
The membrane separation method of the present invention may be
employed to reduce concentration polarization and membrane fouling
to maintain a membrane flux, as well as to obtain concentrated
retention components. Therefore, the membrane separation method of
the present invention may be employed in any membrane separation
process, which produces concentration polarization, such as
membrane concentration, membrane filtration, membrane distillation,
membrane extraction or membrane absorption etc.
In some embodiments of the membrane separation method of the
present invention, said membrane separation method may be a
membrane concentration method, comprising removing a part of the
concentration polarization layer from the separation side to obtain
concentrated retention components. Said membrane concentration
method is particularly suitable for high-efficiency concentration
of biomacromolecules due to the rapid formation of concentration
polarization layer, high concentration degree and moderate
concentration conditions.
In other embodiments of the membrane separation method of the
present invention, said membrane separation method may be a
membrane filtration method, comprising removing the permeation
components form the permeation side to obtain the permeation
components with a reduced retention components. Since the quantity
of the retention components in concentration polarization layer is
reducing, the membrane fouling can be effectively controlled and
the membrane flux can be maintained for a long time. Therefore,
said membrane filtration method can significantly enhance
filtration efficiency and prolong the useful life of the filtration
membrane.
On the other hand, the present invention provides a membrane
separation equipment comprising a separation membrane and a drawer,
in which the drawer is configured to remove at least part of a
concentration polarization layer from a separation side of the
separation membrane during a membrane separation process. In the
present invention, the membrane separation equipment refers to a
membrane separation unit, membrane separation setup, membrane
separation system, membrane separation device or membrane
separation module.
In some embodiments of the membrane separation equipment of the
present invention, said membrane separation equipment further has a
essentially open or enclosed housing, in which the housing together
with the separation membrane are used to isolate the separated
fluid from the permeation components. In other embodiments of the
membrane separation equipment of the present invention, said
membrane equipment has no housing, in which the separation membrane
per se is used to isolate the separated fluid from the permeation
components, and examples thereof can be situations of using
hollow-fiber membranes or tubular membranes.
In some embodiments of the membrane separation equipment of the
present invention, said drawer may be located at the separation
side or the permeation side, inside the separation membrane or on
the separation membrane.
In some embodiments of the membrane separation equipment of the
present invention, said drawer together with the separation
membrane form a membrane module.
In some embodiments of the membrane separation equipment of the
present invention, said drawer comprises a hollow structure having
at least one opening which is located inside the concentration
polarization layer in the separation side of said separation
membrane and allows at least part of the concentration polarization
layer to enter into said hollow structure and to be removed.
In some embodiments of the membrane separation equipment of the
present invention, said hollow structure having opening of said
drawer is a rigid or flexible hollow container. When the opening of
said hollow structure is located inside the concentration
polarization layer, at least part of the concentration polarization
layer is allowed to enter into said hollow structure and to be
removed.
In some embodiments of the membrane separation equipment of the
present invention, said drawer further comprises a channel that
connects said hollow structure and the outside of said
concentration equipment and allows the concentration polarization
layer entering into said hollow structure to be separated from said
concentration equipment.
In some embodiments of the membrane separation equipment of the
present invention, the configuration of said opening makes said
concentration polarization layer be separated from said separation
membrane essentially along the normal or tangential direction of
the separation membrane or any direction between the normal
direction and the tangential direction.
In some embodiments of the membrane separation equipment of the
present invention, the distance and relative position between said
drawer and said separation membrane are fixed or adjustable. For
example, said drawer is fixed or movable with respect to the
separation membrane, while the opening of the hollow structure is
fixedly located inside the concentration polarization layer. For
another example, said drawer is fixed or movable with respect to
the separation membrane, while the opening of the hollow structure
is movable along vertical direction and parallel direction to the
surface of said separation membrane respectively or simultaneously
with respect to the membrane, which allows said opening to enter
inside the concentration polarization layer when needed to draw the
concentration polarization layer at different positions, and to
leave the concentration polarization layer when needed.
In some embodiments of the membrane separation equipment of the
present invention, the opening of the hollow structure of the
drawer may face toward any direction with respect to the separation
membrane, in particular directly face toward the separation
membrane.
In some embodiments of the membrane separation equipment of the
present invention, the section with opening of the hollow structure
of said drawer is present in an essentially planar, cruciate,
spiral, latticed or suspending needle shape, or a combination
thereof. In some embodiments, said section as a whole may
substantially match with the surface of the specific separation
membrane. For example, as for a tabular membrane, said section as a
whole is in an essentially planar shape, while as for a tubular
membrane, said section as a whole is in an annular shape. However,
in any situation, a part of said section may be presented in other
shapes as stated above or a combination thereof.
In some embodiments of the membrane separation equipment of the
present invention, the section with opening of the hollow structure
of said drawer is essentially parallel to the surface of said
separation membrane, i.e. the shortest distances between said
section and said separation membrane are essentially equal at
everyplace.
In some embodiments of the membrane separation equipment of the
present invention, the opening of hollow structure of said drawer
may be holes in any suitable shape, such as essentially round,
slit, polygonal or abnormal shape.
In some embodiments of the membrane separation equipment of the
present invention, the hollow structure of said drawer has at least
one opening, and the number of openings may be determined according
to the material, size and shape of the hollow structure, the size
and shape of the openings, the size and shape of the separation
membrane, the property of retention components, and other specific
application conditions and parameters. When the hollow structure
has more than one opening, these openings may be located regularly
or randomly on the hollow structure of said drawer, in particular
they are located on the surface of hollow structure of said drawer
that faces toward said separation membrane.
In some embodiments of the membrane separation equipment of the
present invention, the opening of the hollow structure of said
drawer may have any suitable size, such as from 0.01 to 5 mm,
preferably from 0.1 to 2.0 mm, more preferably from 0.1 to 0.5
mm.
In some embodiments of the membrane separation equipment of the
present invention, all or part of said drawer may be rigid, elastic
or flexible. Based on different separation membranes, fluids and
operation conditions, all or part of said drawer may be made of any
suitable material selected from metals, such as steel, copper,
aluminum, titanium, nickel, gold, silver, etc., or alloys thereof;
plastics, such as thermoplastics, thermosetting plastics,
engineering plastics, or composites thereof; rubbers, such as
natural rubber, synthetic rubbers, elastomers, or composites
thereof; or a combination thereof.
In some embodiments of the membrane separation equipment of the
present invention, said fluid is a fluid containing components
capable of forming a concentration polarization layer at the
separation side of the separation membrane, for examples, said
fluid can be a solution, a liquid-solid suspensoid, a liquid-liquid
suspensoid, a sol, a gas mixture, a gas-solid suspensoid, a
gas-liquid suspensoid, or an aerosol.
In some embodiments of the membrane separation equipment of the
present invention, said retention components refer to any
components in the fluid, which can be retained at least partially
by the separation membrane, such as one or more solute molecules or
ions, solid particles and liquid droplets etc., in particular
organic or inorganic solutes, more particularly biomacromolecule
such as proteins, nucleic acids and polysaccharide etc. and
biomicromolecule such amino acids, nucleotides and monosaccharides
etc. Said permeation components refer to any components in the
fluid, which can at least partially permeate the separation
membrane, such as one or more liquid solvents, carrier gases, and
components which differ from the retention components such as
molecules or ions. In some embodiments, said retention components
may form a filter cake at the separation side and/or enter into and
block membrane pores and/or permeate the separation membrane, in
addition to the formation of a concentration polarization
layer.
In some embodiments of the membrane separation equipment of the
present invention, said separation membrane refers to any membrane,
which can be used for membrane separation, such as nanofiltration
membrane, ultrafiltration membrane and microfiltration membrane, in
particular nanofiltration, ultrafiltration or microfiltration
membrane made of celluloses, poly(ether sulfone)s, polysulfones,
polyolefins, polyamides, polypiperazidines, metals, glasses or
ceramics.
In some embodiments of the membrane separation equipment of the
present invention, said separation membrane may be present in any
suitable configuration, such as tabular, plate-and-frame, spiral,
tubular or hollow fiber shape.
In some embodiments of the membrane separation equipment of the
present invention, said separation membrane has a suitable
permeation flux, for example, ranging from 1.times.10.sup.-8 m/s to
1.times.10.sup.-4 m/s, preferably from 2.78.times.10.sup.-7 m/s to
1.39.times.10.sup.-4 m/s, more preferably from 1.84.times.10.sup.-6
m/s to 3.69.times.10.sup.-5 m/s.
In some embodiments of the membrane separation equipment of the
present invention, the concentration polarization layer is formed
at the separation side of the separation membrane under the gravity
of a fluid per se. In this case, no additional means is used in
said membrane separation equipment for exerting a driving force on
said fluid.
In some embodiments of the membrane separation equipment of the
present invention, an additional means is used in said membrane
separation equipment for exerting a driving force on said fluid to
form a concentration polarization layer at the separation side of
the separation membrane. Said driving force may be produced by any
suitable means, such as a means causing a pressure difference, a
concentration difference, a potential difference or a temperature
difference, in particular a pressure difference between the
separation side and the permeation side. In particular, a positive
pressure is exerted on the separation side of the membrane or a
negative pressure is exerted on the permeation side of the membrane
by a known means to produce a pressure difference, wherein the
positive pressure may be produced using pump, positive pressure
fluid or centrifugal force etc. at the separation side, while the
negative pressure may be produced by a vacuum means at the
permeation side. A concentration difference may be produced by
means of evaporation, adsorption or dilution using a known means. A
potential difference may be produced by exerting a direct current
between two sides of a membrane using a known means to make the
charged ions or molecules permeate the membrane and migrate to the
electrodes at two sides, thereby forming a concentration
polarization boundary layer at each side of the membrane. A
temperature difference may be produced by a means capable of
controlling the fluids of both sides at different temperatures,
such as heater, cooler or heat exchanger.
In some embodiments of the membrane separation equipment of the
present invention, said membrane separation equipment is a dead-end
filtration equipment, comprising a dead-end filtration cell, a
filtration membrane as a separation membrane and a drawer for
drawing a concentration polarization layer, wherein said filtration
membrane is located at the bottom of the dead-end filtration cell,
the drawer is located in the dead-end filtration cell, one end of
said drawer is located outside of the dead-end filtration cell, the
other end of said drawer is a hollow structure essentially in
planar, cruciate, spiral, latticed, suspending needle or other
shape, is essentially parallel to the surface of said filtration
membrane, and is located inside the concentration polarization
layer on the filtration membrane surface, wherein said hollow
structure has at least one opening on one end near to the
filtration membrane surface, and the at least one opening is
preferably one or more holes having a diameter ranging from 0.01 to
5 mm, preferably ranging from 0.1 to 0.5 mm.
In some embodiments of the membrane separation equipment of the
present invention, said membrane separation equipment is a
plate-and-frame filtration equipment comprising plate membrane
elements for separation and drawers for drawing concentration
polarization layers, wherein said plate membrane elements are in
parallel and each of the drawers for drawing concentration
polarization layer is configured in close proximity to the surface
of one of said plate membrane elements, and each of said drawers
has a plate latticed hollow structure having at least one opening
on a side thereof near to the filtration membrane surface, the at
least one opening is preferably one or more holes having a diameter
ranging from 0.01 to 5 mm, preferably ranging from 0.1 to 0.5 mm,
and each of the drawers is fluidly communicated with a hollow pipe
going outside the concentration equipment.
In some embodiments of the membrane separation equipment of the
present invention, said membrane separation equipment is a
plate-hydraulic static press filtration equipment, comprising a
container, plate membrane filtration elements for separation, and
drawers for drawing concentration polarization layers, wherein one
or more parallel palate membrane elements are configured in said
container and each of the drawers for drawing concentration
polarization layer is configured in close proximity to the surface
of one of said plate membrane elements, each of said drawers is a
hollow structure that is present in essentially planar, cruciate,
spiral, latticed, suspending needle or other shape and has at least
one opening on a side thereof near to the filtration membrane
surface, the at least one opening is preferably one or more holes
having a diameter ranging from 0.01 to 5 mm, preferably ranging
from 0.1 to 0.5 mm, and each of the drawers is fluidly communicated
with a hollow pipe going outside the concentration equipment.
In some embodiments of the membrane separation equipment of the
present invention, said membrane separation equipment is a
plate-suction equipment comprising a container, plate membrane
filtration elements for separation, and drawers for drawing
concentration polarization layers, wherein one or more parallel
plate membrane elements are configured in said container, and each
of the drawers for drawing concentration polarization layer is
configured in close proximity to the surface of one of said plate
membrane elements, wherein each of said drawers is a hollow
structure that is present in essentially planar, cruciate, spiral,
latticed, suspending needle or other shape and has at least one
opening on a side thereof near to the filtration membrane surface,
the at least one opening is preferably one or more holes having a
diameter ranging from 0.01 to 5 mm, preferably ranging from 0.1 to
0.5 mm, and each of the drawers is fluidly communicated with a
hollow pipe going outside the concentration equipment.
In further another aspect, the present invention provides a drawer
for drawing a concentration polarization layer from a separation
side of a separation membrane during separation process, in which
the drawer comprises a hollow structure having at least one
opening, and the drawer is configured to make said opening be
operably located inside the concentration polarization layer at the
separation side of said separation membrane and operably allow at
least part of the concentration polarization layer to pass through
said opening and enter into said hollow structure, thereby removing
at least part of the concentration polarization layer.
In some embodiments of the drawer of the present invention, said
drawer further comprises a channel fluidly communicating said
hollow structure, and the configuration of the channel allows the
concentration polarization layer entering into said hollow
structure to leave said hollow structure.
In some embodiments of the drawer of the present invention, said
drawer together with the separation membrane form a membrane
module.
In some embodiments of the drawer of the present invention, the
configuration of said opening allows said concentration
polarization layer to be separated from said separation membrane
essentially along the normal or tangential direction of the
separation membrane, or any direction between the normal direction
and the tangential direction.
In some embodiments of the drawer of the present invention, said
hollow structure is a rigid or flexible hollow container.
In some embodiments of the drawer of the present invention, said
drawer further comprises a connection means, and the configuration
of said connection means allows the distance and the relative
position between said drawer and said separation membrane to be
fixed or alterable. For example, said connection means is a
bracket, cantilever, hinge, rail or lever, after being configured,
it allows said drawer to be fixed or movable with respect to the
separation membrane. Therefore, the opening of said hollow
structure is fixed and located inside the concentration
polarization layer all the time with respect to said separation
membrane, or said opening is operably movable along the vertical
direction and parallel direction with respect to the surface of
said separation membrane separately or simultaneously, which allows
said opening to enter inside the concentration polarization layer
when the draw of concentration polarization layer at different
positions is necessary, and to leave the concentration polarization
layer when needed.
In some embodiments of the drawer of the present invention, the
opening of the hollow structure of the drawer may face toward any
direction with respect to the separation membrane, in particular
directly face toward the separation membrane.
In some embodiments of the drawer of the present invention, the
section with opening of the hollow structure is present in
essentially planar, cruciate, spiral, latticed, suspending needle
shape, or a combination thereof, wherein said opening is located on
the most projecting position, lateral position or cavate position
of said section. For example, as for a tabular membrane, said
section as a whole is essentially in planar shape, while as for a
tubular membrane, said section as a whole is in annular shape.
However, in any situation, a part of said section may have other
abovementioned shapes or a combination thereof.
In some embodiments of the drawer of the present invention, the
section with opening of the hollow structure is essentially
parallel to the surface of said separation membrane, i.e. the
shortest distances between said section and said separation
membrane are essentially equal at everyplace.
In some embodiments of the drawer of the present invention, the
section with opening of the hollow structure as a whole may
substantially match with the surface of the specific separation
membrane. For example, as for a plate membrane, said section as a
whole is essentially in planar shape, while as for a tubular
membrane, said section as a whole is in annular shape. However, in
any situation, a part of said section may have other abovementioned
shapes or a combination thereof.
In some embodiments of the drawer of the present invention, said
drawer may essentially cover at least part of the separation
surface of the separation membrane in a fixed or movable manner. In
other embodiments of the drawer of the present invention, said
drawer may cover substantially the whole separation surface of the
separation membrane in a fixed or movable manner, i.e. the opening
of the hollow structure of said drawer may essentially reach the
whole separation surface of said separation membrane. However, in
further embodiments of the drawer of the present invention, said
opening may reach at least part of the separation surface of said
separation membrane.
In some embodiments of the drawer of the present invention, the at
least one opening of the hollow structure of said drawer may be a
hole in any suitable shape such as essential round, slit, polygonal
or abnormal shape.
In some embodiments of the drawer of the present invention, the
hollow structure of said drawer has at least one opening, and the
number of opening may be determined according to the material, size
and shape of the hollow structure of the drawer, the size and shape
of the opening, the size and shape of the separation membrane, the
property of retention components, and other specific application
conditions and parameters. When the hollow structure has more than
one opening, these openings may be located regularly or randomly on
the hollow structure of said drawer, for example, they are located
on the surface of the hollow structure of said drawer that faces
toward said separation membrane.
In some embodiments of the drawer of the present invention, the
opening of the hollow structure of said drawer may have any
suitable size, such as from 0.01 to 5 mm, preferably from 0.1 to
2.0 mm, more preferably from 0.1 to 0.5 mm.
In some embodiments of the drawer of the present invention, all or
part of said drawer may be rigid, elastic or flexible. Based on
different separation membranes, fluids and operation conditions,
all or part of said drawer may be made of any suitable material
selected from metals such as steel, copper, aluminum, titanium,
nickel, gold, silver, etc., or alloy thereof; plastics, such as
thermoplastics, thermosetting plastics, engineering plastics or
composites thereof; rubbers, such as natural rubber, synthetic
rubbers, elastomers or composites thereof; or a combination
thereof.
In some embodiments of the drawer of the present invention, said
drawer is made of a silicone rubber by a microprocessing
technique.
In other embodiments of the present invention, unless otherwise
stated, any technical solution as stated above and the technical
features thereof can be applied singly or in any combination, which
is obvious for a person skilled in the art who has read the present
invention.
The present invention will be further illustrated by the
concentration of biomacromolecules using ultrafiltration, but will
not be restricted thereby. Herein, the membrane separation may also
be called filtration, membrane filtration, ultrafiltration,
concentration, membrane concentration or ultrafiltration
concentration, the concentration polarization layer may also be
called concentrate liquid, the fluid may also be called solution,
material liquor or raw material liquor, the retention component may
also be called solute, the membrane separation equipment may also
be called equipment or filtration equipment, and the separation
membrane may also be called filtration membrane or membrane
element.
Ultrafiltration concentration as a membrane separation technique
can be used to separate substances having a molecular weight
ranging from 1,000 to 1000,000, has no phase transition in
separation process, can be carried out under moderate separation
conditions, and can maintain the activity of biomacromolecules, so
that it is specifically suitable for the concentration and
desalinization of biological products such as proteins,
polysaccharides, enzymes, nucleic acids, DNAs and monoclonal
antibodies. In addition, since ultrafiltration concentration has
advantages of low cost, simple operation, easy to be scaled up and
high recovery rate, it is widely applied in biotechnological
industry. A dead-end filtration technology or a cross-flow
filtration technology has been generally employed in
ultrafiltration concentration process. Dead-end filtration is
similar to sand filtration, in which material liquor passes through
the surface of a membrane vertically, all retained substances
accumulate on the surface of membrane, while solvent and
micromolecule substances permeate the membrane. Since the retained
substances accumulate on the membrane surface continuously, the
total resistance of filtration increases continuously, which
results in a severe membrane fouling and a gradual decrease in
membrane flux. Consequently, the membrane has to be cleaned
frequently. When a cross-flow filtration technology is employed,
the bulk phase of a material liquor flows in parallel with the
membrane surface, the permeation liquid permeates the membrane
vertically, and the material liquor with a high tangential velocity
can take the substances deposited on membrane surface away, thereby
slowing the speed of increase in filtration resistance. However,
the application of cross-flow filtration to shear-sensitive
biomacromolecules is restricted due to its high tangential velocity
of material liquor on the membrane surface. It can be seen that
whatever filtration mode is employed, membrane fouling cannot be
avoided.
The main factors affecting concentration polarization and
concentration polarization layer during ultrafiltration process
include transmembrane pressure, filtration mode, feeding rate and
properties of solution such as pH value, ionic strength, diffusion
coefficient of solute and viscosity of solution etc. The
concentration of solute in a concentration polarization layer may
be hundreds times higher than that in bulk phase by adjusting these
factors, and even the concentration of solute may be higher than
the dissolubility of the solute in the solvent, thus resulting in
solute precipitating on membrane surface. A great number of studies
show that a relatively stable concentration polarization layer may
be formed within one or several minutes.
The membrane separation method and equipment provided by the
present invention can be used to concentrate biomacromolecules and
organic micromolecules (such as saccharides, organic acids and
polypeptides etc.) in order to overcome the shortcomings of the
conventional ultrafiltration concentration process, such as severe
membrane fouling, easy to inactivate biomacromolecules, frequent
cleaning of membrane and difficult to operate continuously. etc.
The method comprises the adjustment of the thickness of
concentration polarization layer on membrane surface and the
concentration and distribution of solute in the concentration
polarization layer by controlling the operation conditions, such as
permeation flux, concentration of material liquor, drawing rate and
transmembrane pressure etc., to obtain optimal concentration
effects. Wherein, the permeation flux of a filtration membrane may
range from 1.84.times.10.sup.-6 m/s to 3.69.times.10.sup.-5 m/s,
the concentration of a material liquor may range from 1.0 mg/L to
1000 mg/L, the drawing rate may depend on the properties of raw
material liquor and concentration requirements and be 1/2 to 1/1000
of the flux of raw material liquor fed into the membrane
concentration equipment, and the transmembrane pressure may range
from 0.01 MPa to 4 MPa.
Said biomacromolecules include proteins, polypeptide, amino acids,
polysaccharides, RNAs and deoxyribonucleic acids etc, and said
organic micromolecules include sugar, organic acids and
polypeptides etc.
In the present invention, the equipments useful for a membrane
filtration process utilizing concentration polarization to
concentrate biomacromolecules include but are not limited to:
dead-end filtration equipment, plate-and-frame cross-flow
filtration equipment, plate-hydraulic static press filtration
equipment and plate-suction filtration equipment, while the
equipments useful for a membrane filtration process to concentrate
organic micromolecules such as sugar, organic acids and
polypeptides etc. include but are not limited to: dead-end
filtration equipment and plate-and-frame cross-flow filtration
equipment.
Said dead-end filtration equipment comprises: a dead-end filtration
cell, a filtration membrane, a drawer for drawing concentrated
liquid, pressure sensors, a feeding pump, and an injection pump or
a constant flow pump. A tabular filtration membrane is located on
the bottom of the dead-end filtration cell, and the drawer for
drawing concentrated liquid is located in the dead-end filtration
cell, wherein one end of said drawer extends outside the dead-end
filtration cell and connects with the injection pump or constant
flow pump, and the other end of said drawer is a hollow structure
in cruciate or spiral shape and is parallel and close to the
filtration membrane surface, wherein said hollow structure has a
plurality of openings on a side thereof near to the filtration
membrane surface. A raw material inlet is on the top of the
dead-end filtration cell, and a permeation liquid outlet is under
the filtration membrane in the dead-end filtration cell.
Said dead-end filtration cell is a tabular membrane filter and is
designed as a short and stout device, and a pressure sensor is set
at the raw material side.
A pipeline accompanied with a pressure sensor is mounted on the raw
material inlet, and connects with the feeding pump.
Said openings have a diameter ranging from 0.1 to 0.5 mm.
Said drawer for drawing the concentrated liquid is made of a hollow
plastic or silicone pipe having an external diameter ranging from
0.5 to 1.5 mm by a microporcessing technique, and its one end is a
hollow pipe structure in cruciate or spiral shape and has a
plurality of holes with a diameter ranging from 0.1 to 0.5 mm on a
side thereof near to the filtration membrane surface. Said drawer
for drawing the concentrated liquid connects with the injection
pump or constant flow pump outside the filtration cell to exactly
draw the concentrated liquid at a desired flux from the dead-end
filtration cell. According to the properties of biomacromolecules
and organic micromoelcules to be concentrated, the filtration
membrane of the present invention is typically selected from
microfiltration membrane, ultrafiltration membrane or
nanofiltration membrane made of celluloses, poly(ether sulfone)s,
polysulfones, polyamides or polypiperazidines etc.
Said plate-and-frame cross-flow filtration equipment comprises:
plate membrane elements, drawers for drawing concentrated liquid,
pressure sensors, a feeding pump, an injection pump or a constant
flow pump and cut-off valves. The plate-and-frame cross-flow
filtration equipment contains a plurality of parallel plate
membrane elements, and a drawer for drawing concentrated liquid is
configured in close proximity to the surface of each of said plate
membrane elements. Each of said drawers has a plate latticed hollow
structure having a plurality of openings with a diameter ranging
from 0.1 to 5 mm at a side thereof near to the filtration membrane
surface and connects with a hollow pipe at one end thereof. After
the hollow pipe of each drawer is connected in parallel, it extends
outside the plate-and-frame cross-flow filtration equipment and
connects with the injection pump or constant flow pump. A raw
material inlet is set on one side of the plate-and-frame cross-flow
filtration equipment, a pipeline accompanied with a cut-off valve
and a pressure sensor is mounted on the raw material inlet, wherein
said pipeline connects with the feeding pump. A material liquid or
circulating liquid outlet is on the other side of the
plate-and-frame cross-flow filtration equipment, and the outlet
connects with a pipeline accompanied with a cut-off valve, wherein
said pipeline connects with a raw material tank. When the equipment
is run, the cut-off valve in said pipeline shuts off; when the
membrane need cleaning, the valve opens up for cross-flow cleaning.
A permeation liquid outlet is on each of the plate membrane
elements. After the permeation liquid from each outlet is connected
in parallel, it is discharged from the plate-and-frame cross-flow
filtration equipment.
Said drawer for drawing concentrated liquid is made of a hollow
plastic or silicone pipe having an external diameter ranging from
0.5 to 1.5 mm by a microporcessing technique, and it is a
plate-latticed hollow structure having a plurality of openings with
a diameter ranging from 0.1 to 0.5 mm at a side thereof near to the
filtration membrane surface. An end of said drawer connects with a
hollow pipe to discharge the concentrated liquid.
According to the properties of biomacromolecules and organic
micromoelcules to be concentrated, the filtration membrane of the
present invention is typically selected from microfiltration
membrane, ultrafiltration membrane or nanofiltration membrane made
of celluloses, poly(ether sulfone)s, polysulfones, polyamides or
polypiperazidines etc.
Said plate-hydraulic static press filtration equipment comprises: a
high-level feed tank, a membrane filtration tank, a liquid level
meter, plate membrane elements, drawers for drawing concentrated
liquid, pressure sensors, a feeding pump, an injection pump or a
constant flow pump and cut-off valves. A plurality of parallel
palate membrane elements are configured in the membrane filtration
tank and a drawer for drawing concentrated is configured in close
proximity to the surface of each of said plate membrane elements.
Each of said drawer has a plate latticed hollow structure having a
plurality of openings with a diameter ranging from 0.1 to 5 mm at a
side thereof near to the filtration membrane surface and connects
with a hollow pipe. One end of each of said drawer connects with a
hollow pipe. After the hollow pipe of each drawer is connected in
parallel, it extends outside the plate-hydraulic static press
filtration equipment and connects with the injection pump or
constant flow pump. A permeation liquid outlet is on each of the
plate membrane elements, and the permeation liquid outlets are
connected with each other in parallel, and then fluidly connected
with a pipeline accompanied with a pressure sensor and a cut-off
valve. A transmembrane pressure of permeation liquid is provided by
a hydrostatic water head controlled by the liquid level meter of
the membrane filtration tank. A raw material inlet is configured on
the membrane filtration tank, and the inlet connects with a
pipeline accompanied with a cut-off valve and a high-level feed
tank. The structure of the drawer for drawing concentrated liquid
and the selection of filtration membrane are identical to those
described for a plate cross-flow filtration equipment.
Said plate suction filtration equipment comprises: a membrane
filtration tank, a liquid level meter, plate membrane elements,
drawers for drawing concentrated liquid, pressure sensors, a
feeding pump, an injection pump or a constant flow pump, a suction
pump and cut-off valves. A plurality of parallel palate membrane
elements are configured in the membrane filtration tank and a
drawer for drawing concentrated liquid is configured in close
proximity to the surface of each of said plate membrane elements.
Each of said drawer has a plate latticed hollow structure having
openings with a diameter ranging from 0.1 to 5 mm at a side thereof
near to the filtration membrane surface and connects with a hollow
pipe. One end of each of said drawer connects with a hollow pipe.
After the hollow pipe of each drawer is connected in parallel, it
extends outside the plate suction filtration equipment and connects
with the injection pump or constant flow pump. A permeation liquid
outlet is configured on each of plate membrane elements, and the
permeation liquid outlets are connected with each other in
parallel, and then fluidly connected with a pipeline accompanied
with a pressure sensor, a cut-off valve and a suction bump. A raw
material inlet is configured on the membrane filtration tank, and
the inlet connects with a pipeline accompanied with a cut-off valve
and a feeding pump. The structure of the drawer for drawing
concentrated liquid and the selection of filtration membrane are
identical to those described for a plate cross-flow filtration
equipment.
As compared with a conventional ultrafiltration concentration
process, the method for concentrating biomacromolecules and organic
micromolecules utilizing concentration polarization according to
the present invention has the following outstanding characteristics
and advantages: (1) By utilizing the concentration polarization, a
good effect of enriching a solute is obtainable even if the
concentration of a solute in bulk phase is relatively low, thereby
greatly enhancing the concentration rate and efficiency. (2) During
the concentration process, the concentrated liquid is discharged
from the membrane filtration equipment, so that the potential
membrane fouling substances together with the concentrated liquid
are discharged from the membrane unit, thereby effectively reducing
the potentiality of membrane fouling and greatly decreasing the
frequency of cleaning membrane. Therefore, the double functions of
concentrating solute and slowing membrane fouling are obtained. (3)
The equipment, technology and operation of the membrane
concentration of the present invention are simple, and continuous
or semi-continuous operation can be realized and the service life
of the membrane further increased at the same time. (4) The
concentration process is performed without shearing force or under
a low shearing force, thereby largely reducing energy consumption
and effectively decreasing the risk of inactivation and
denaturation of biomacromolecules caused by shearing force,
therefore the method of the present invention is especially
suitable for the concentration of shear-sensitive
biomacromolecules.
In the present invention, a concentration polarization layer is
directly removed from a membrane surface, which not only decreases
the adverse influences of concentration polarization on membrane
separation but also obtains a highly concentrated retention
components, thereby significantly improving the ability to maintain
membrane flux, lessening concentration polarization and membrane
fouling during membrane separation process, and achieving the high
concentration of the retention components.
In the present invention, the term "fluid" should be interpreted in
the broadest sense, which includes but is not limited to a gas, a
liquid, a colloid, a solution, a molecular solution, a liquid-solid
suspensoid, a liquid-liquid suspensoid, a sol, a gas mixture, a
gas-solid suspensoid, a gas-liquid suspensoid, an aerosol, or a
combination thereof, and is a fluid containing components capable
of forming a concentration polarization layer at the separation
side of a separation membrane.
In the present invention, the term "retention component" should be
interpreted as the fluid component that cannot essentially permeate
a separation membrane, and the term "permeation component" as the
fluid component that can essentially permeate a separation
membrane. That is to say, even if the "retention component" can
permeate a separation membrane, its permeation rate is far lower
than that of the "permeation component", thereby enriching the
"retention component" at separation side.
In the present invention, the term "membrane separation" refers to
an operation or process for reducing or removing one or more
components in a raw material using a selective permeation membrane
to increase the proportion or concentration of other one or more
components in the raw material.
In the present invention, the term "concentration polarization"
refers to a phenomenon that a separation membrane selectively
allows some components in a raw material to pass through but other
components to be retained, which results in the enriching of the
retention components near to the membrane surface of separation
side to form a concentration gradient from membrane surface to raw
material bulk phase. In theory, any boundary layer in which a
concentration gradient of retention component from membrane surface
to raw material bulk phase exists may be called "concentration
polarization layer".
DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic diagram of a dead-end membrane filtration
device for concentrating biomacromolecules and organic
micromolecules utilizing concentration polarization.
FIG. 2 is a schematic diagram of a plate-and-frame cross-flow
membrane filtration device for concentrating biomacromolecules and
organic micromolecules utilizing concentration polarization.
FIG. 3 is a schematic diagram of a plate suction membrane
filtration device for concentrating biomacromolecules and organic
micromolecules utilizing concentration polarization.
FIG. 4 is a schematic diagram of a plate hydraulic static press
membrane filtration device for concentrating biomacromolecules and
organic micromolecules utilizing concentration polarization.
EXAMPLES
The present invention is further illustrated in conjunction with
the following examples, while the protection scope as claimed in
the present invention is not limited to these examples.
Example 1
Turning to FIG. 1, the equipment for a dead-end membrane filtration
process of concentrating biomacromolecules and organic
micromolecules utilizing concentration polarization comprised: a
dead-end filtration cell 3, a filtration membrane 2, a drawer 1 for
drawing a concentrated liquid, a pressure sensor 4, a feeding pump
5, and an injection pump or constant flow pump 6.
The dead-end filtration cell 3 had an effective membrane area of
4.45 cm.sup.2 and a volume of 6.7 mL. The tabular filtration
membrane 2 was located on the bottom of the dead-end filtration
cell, wherein the filtration membrane was Ultracel PL
ultrafiltration membrane of regenerated cellulose with a molecular
weight cut-off of 10 KD and a high recovery rate (Millipore
Company). The drawer 1 made of a hollow plastic or silicone pipe
having an external diameter ranging from 0.5 to 1.5 mm was
configured on the filtration membrane surface, wherein one end of
said drawer extended outside the dead-end filtration cell 3 and was
connected with the injection pump 6, and the other end of said
drawer connected with a cruciate hollow pipe which communicated
with the main pipe of the drawer. The cruciate hollow pipe was
parallel and in close proximity to the filtration membrane surface
and had several holes with a diameter ranging from 0.1 to 0.5 mm. A
raw material inlet was on the top of the dead-end filtration cell
3. A pipeline accompanied with the pressure sensor 4 was configured
on the raw material inlet. The pipeline connected with the feeding
pump 5. A permeation liquid outlet was set at the lower part of the
dead-end filtration cell 3 under the filtration membrane.
A feed solution containing 0.5 g/L of bovine serum albumin (BSA)
(Mb=68 KD, purity>98%) was fed continuously into the dead-end
filtration cell. The permeation flux of the filtration membrane was
3.745.times.10.sup.-6 m.sup.3/(m.sup.2s) (0.1 mL/min). After the
feed solution had been filtrated and concentrated for 1 hour, the
injection pump run to continuously draw the concentrated BAS
solution in the concentration polarization layer by the drawer for
drawing the concentrated liquid near to the filtration membrane
surface at a drawing rate of about 300 .mu.L/h. The permeation
liquid was discharged from the outlet under the filtration membrane
in the dead-end filtration cell.
The results obtained from a conventional dead-end filtration
concentration (i.e. a dead-end filtration method without drawing
the concentrated liquid) were compared with the results obtained
from the membrane concentration method of the present invention.
The results showed that: after continuous filtration concentration
operation for 6.5 hours, the concentration of BSA in the
concentrated liquid obtained from the method of the present
invention was 6.6 g/L and 13.2 times as the BSA concentration in
the feed, while the concentration of BSA in the concentrated liquid
obtained from the conventional membrane concentration method was
only 3.2 g/L and 6.4 times as the BSA concentration in the feed;
when the conventional membrane concentration method was employed,
the transmembrane pressure (TMP) of the system reached the limit
value (1.0 MPa) of the equipment after 6.5 hours operation, while
when the membrane filtration method of the present application was
employed, the TMP slowly increased and was only 20% of that in the
conventional membrane concentration method after 6.5 hours. In
addition, the test results of membrane resistance after filtration
showed that there was essentially no change in the membrane
resistance before and after filtration when the membrane
concentration method of the present invention was employed, while
the membrane resistance increased by more than 20% after filtration
when the conventional ultrafiltration concentration was employed.
Clearly, the application of the present invention shows a good
concentration effect, and can effectively control the membrane
fouling and facilitate long-term stable operation during membrane
concentration process.
Example 2
The method and equipment used were the same as those in Example 1,
while the concentration of BSA in a feed solution (C.sub.f) was 0.5
g/L and the permeation flux (J.sub.v) of the filtration membrane
was 3.745.times.10.sup.-6 m.sup.3/(m.sup.2s). When the TMP
increased to 100 KPa and 150 KPa, the concentrated liquid was drawn
at a drawing rate of 360 .mu.L/h and 420 .mu.L/h, respectively. At
the initial stage of drawing, the TMP under both experimental
conditions decreased, and then it could be stabilized at 60 and 107
KPa for a long period of time, respectively, suggesting that
membrane fouling was effectively controlled during concentration
process and the concentration operation could be stably conducted
for a long period of time. After operation for 8 hours, the average
concentrations of BSA in the concentrated liquids obtained by
drawing were 8.9 and 7.0 g/l, i.e., 17.8 and 14.0 times as that in
the feed, respectively.
Example 3
The method and equipment used were the same as those in Example 1,
while the concentration of BSA in a feed solution (C.sub.f) was 0.5
g/L and the permeation flux (J.sub.v) of the filtration membrane
was 3.745.times.10.sup.-6 m.sup.3/(m.sup.2s). In order to obtain a
concentrated liquid with a higher concentration, an intermittent
drawing mode was used to draw the concentrated liquid. The drawing
operation started up at a TMP of 100 and 150 KPa and a drawing rate
of 360 .mu.L/h and 420 .mu.L/h, respectively. Such operation
stopped when the TMP decreased to 60 and 107 KPa respectively. When
the TMP again reached the values for initiating the drawing, the
concentrated liquid was drawn at the same rates again. The above
operations were conducted repeatedly. After operation for 8 hours,
the concentrations of BSA in the concentrated liquid obtained by
the drawing were 11.8 and 12.4 g/l, i.e., 23.6 and 24.8 times as
that in the feed, respectively. Clearly, the multiple intermittent
drawing operation mode facilitates the acquirement of a
concentrated liquid with a high concentration, the TMP was
controllable at the same time, and the average TMP of system was
more or less constant.
Example 4
The method and equipment used were the same as those in Example 1,
while the concentration of BSA in a feed solution (C.sub.f) was 0.5
g/L and the permeation flux (J.sub.v) of the filtration membrane
was 3.745.times.10.sup.-6 m.sup.3/(m.sup.2s). An intermittent
drawing mode was used to draw the concentrated liquid. When the TMP
increased to 100 KPa, the concentrated liquid was drawn at a
drawing rate of 360 .mu.L/h for a drawing time of 30, 10 or 5
minutes, respectively. The drawing operation stopped after the
above predetermined drawing time. When the TMP increased to 100 KPa
again, the drawing operation started up again. The above operations
were conducted repeatedly. The results showed that when the drawing
time was 5 minutes, the concentration of BSA in the concentrated
liquid obtained was 34.9 g/L and 69.8 times as that in the feed;
when the drawing time was 10 and 30 minutes, the concentrations of
BSA in the concentrated liquids obtained were 31.5 and 19.0 g/L,
i.e., 63.0 and 38.0 times as that in the feed, respectively. During
the entire drawing operation, the TMP was controllable, the average
TMP of system was more or less constant, indicating that membrane
fouling was effectively controlled during the concentration and a
continuous concentration operation could be achieved.
Example 5
Turning to FIG. 2, an equipment for a plate-and-frame cross-flow
membrane filtration process of concentrating biomacromolecules and
organic micromolecules utilizing concentration polarization
comprised: plate membrane elements 1, drawers 2 for drawing a
concentrated liquid, a pressure sensor 4, a feeding pump 5, an
injection pump or constant flow pump 3, and cut-off valve 6.
The plate-and-frame cross-flow filtration equipment contained three
parallel plate membrane elements 1, wherein each of the membrane
elements had an effective membrane area of 0.03 m.sup.2, and the
filtration membrane was a polysulfone ultrafiltration membrane with
a molecular weight cut-off of 50 KD (Alfa laval company in Sweden).
The drawer 2 for drawing the concentrated liquid was configured in
close proximity to the surface of each of said plate membrane
elements 1. The drawer 2 made of a hollow plastic or silicone pipe
with an external diameter ranging from 0.5 to 1.5 mm had a plate
latticed hollow structure having a plurality of holes with a
diameter ranging from 0.1 to 0.5 mm at a side thereof towards the
filtration membrane surface and connected with a hollow pipe at one
end of each drawer. The hollow pipe of each drawer was connected in
parallel and extended outside the plate-and-frame cross-flow
filtration equipment and connected with the injection pump 3
through a collection pipe. A raw material inlet was set on the
plate-and-frame cross-flow filtration equipment, and a pipeline
accompanied with a pressure sensor 4 was mounted on the raw
material inlet, wherein said pipeline connected with the feeding
pump 5. A circulating liquid outlet was set in the filtration
device of the plate-and-frame cross-flow filtration equipment, and
the outlet connected with a pipeline accompanied with a cut-off
valve 6, wherein said pipeline connected with a raw material tank.
A permeation liquid outlet was set on each of the plate membrane
elements 1. After permeation liquid from each outlet was connected
in parallel, it was discharged from the plate-and-frame cross-flow
filtration equipment.
A feed solution containing 0.5 g/L of .gamma.-globulin (Mb=156 KD,
purity>98%) was fed continuously into the plate-and-frame
cross-flow filtration equipment. The TMP of system was maintained
at 100 KPa. An intermittent drawing operation mode was employed to
draw the concentrated liquid. When the permeation flux of system
reached 5.25.times.10.sup.-6 m.sup.3/(m.sup.2s), the concentrated
liquid was drawn at a drawing rate of 18 mL/h for a drawing time of
30, 10 or 5 minutes. The drawing operation stopped after the above
predetermined drawing time. When the permeation flux again reached
5.25.times.10.sup.-6 m.sup.3/(m.sup.2s), the drawing operation
started up again. The above operations were conducted repeatedly.
The results showed that when the drawing time was 5 minutes, the
concentration of .gamma.-globulin in the concentrated liquid
obtained was 25.3 g/L, i.e., 50.6 times as that in the feed; when
the drawing time was 10 and 30 minutes, the concentrations of
.gamma.-globulin in the concentrated liquids obtained were 22.6 and
13.4 g/L, i.e., 45.2 and 26.8 times as that in the feed,
respectively. During the entire drawing operation, the average
permeation flux of system was more or less constant at a relatively
higher level, indicating that the membrane fouling was effectively
controlled during the concentration and a long time concentration
operation could be achieved.
Example 6
Turning to FIG. 3, an equipment for an a plate suction membrane
filtration process for concentrating biomacromolecules and organic
micromolecules utilizing concentration polarization comprised: a
membrane filtration tank 1, plate membrane elements 2, drawers 3
for drawing concentrated liquid, a pressure sensor 5, a feeding
pump 7, an injection pump or a constant flow pump 4, and a sucking
pump 5. Three parallel palate membrane elements 2 were configured
in the membrane filtration tank 1, wherein each of the membrane
elements had an effective membrane area of 0.03 m.sup.2, and the
filtration membrane was a polysulfone ultrafiltration membrane with
a molecular weight cut-off of 50 KD (Alfa laval company in Sweden).
The drawer 3 for drawing concentrated liquid was configured in
close proximity to the surface of each of said plate membrane
elements 2. The drawers 3 made of a hollow plastic or silicone pipe
with an external diameter ranging from 0.5 to 1.5 mm had a plate
latticed hollow structure having a plurality of holes with a
diameter ranging from 0.1 to 0.5 mm at a side thereof towards the
filtration membrane surface and connected with a hollow pipe at one
end of each drawer. The hollow pipe of each drawer was connected in
parallel and extended outside the membrane filtration tank 1 and
connected with the injection pump 4 through a collection pipe. A
permeation liquid outlet was set on each of the plate membrane
elements 2, connected with other permeation liquid outlets in
parallel, and then fluidly connected with a pipeline accompanied
with the pressure sensor 5 and the sucking pump 6. A raw material
inlet was configured on the membrane filtration tank 1, and
connected with a pipeline accompanied with the feeding pump 7.
A feed solution containing 0.5 g/L of .gamma.-globulin (Mb=156 KD,
purity>98%) was fed continuously into the raw membrane
filtration and the plate membrane elements were entirely submerged.
The permeation flux of system was maintained at
5.25.times.10.sup.-6 m.sup.3/(m.sup.2s). An intermittent suction
operation mode was used to draw the concentrated liquid. When the
TMP of system reached 100 Kpa, the concentrated liquid was drawn at
a drawing rate of 24 mL/h for a drawing time of 30, 10 or 5
minutes. The drawing operation stopped after the above
predetermined drawing time. When the TMP again reached 100 KPa, the
drawing operation started up again. The above operations were
conducted repeatedly. The results showed that when the drawing time
was 5 minutes, the concentration of .gamma.-globulin in the
concentrated liquid obtained was 27.4 g/L, i.e., 54.8 times as that
in the feed; when the drawing time was 10 and 30 minutes, the
concentrations of .gamma.-globulin in the concentrated liquids
obtained were 23.9 and 15.0 g/L, i.e., 47.8 and 30.0 times as that
in the feed. During the entire drawing operation process, the TMP
was controllable and the average TMP of system was more or less
constant, suggesting that the equipment could run for a long period
of time.
Example 7
Turning to FIG. 4, an equipment for an a plate hydraulic static
press membrane filtration process for concentrating
biomacromolecules and organic micromolecules utilizing
concentration polarization comprised: plate membrane elements 1,
drawers 2 for drawing concentrated liquid, a membrane filtration
tank 3, an injection pump or a constant flow pump 4, a pressure
gauge 5 and a high level tank 6.
Three parallel palate membrane elements 1 were configured in the
membrane filtration tank 3, wherein each of the membrane elements 1
had an effective membrane area of 0.03 m.sup.2, and the filtration
membrane was a polysulfone unitrfiltration membrane with a
molecular weight cut-off of 50 KD (Alfa laval company in Sweden).
The drawer 2 for drawing concentrated liquid was configured in
close proximity to the surface of each of said plate membrane
elements 1. The drawers made of hollow plastic or silicone pipes
having an external diameter ranging from 0.5 to 1.5 mm had a plate
latticed hollow structure having a plurality of holes with a
diameter ranging from 0.1 to 0.5 mm at a side thereof towards the
filtration membrane surface and connected with a hollow pipe at the
end of each drawer. The hollow pipe of each drawer was connected in
parallel and extended outside the membrane filtration tank 3, and
connected with the injection pump 4 through a collection pipe. A
permeation liquid outlet was configured on each of the plate
membrane elements 1, connected with other permeation liquid outlets
in parallel, and then fluidly connected with a pipeline accompanied
with the pressure gauges. A raw material inlet was set on the
membrane filtration tank 3, and connected via a pipeline with the
high level tank 6. The TMP was provided by a hydrostatic water head
in the membrane filtration tank 3.
A feed solution containing 0.5 g/L of .gamma.-globulin (Mb=156 KD,
purity>98%) was fed continuously into the membrane filtration
tank and the plate membrane elements were entirely submerged. The
position of the membrane elements were controlled to make the
pressure gauge show 10 Kpa, and the initial permeation flux of
system was 0.98.times.10.sup.-6 m.sup.3/(m.sup.2s). An intermittent
drawing operation mode was employed to draw the concentrated
liquid. When the permeation flux of system reached
0.45.times.10.sup.-6 m.sup.3/(m.sup.2s), the concentrated liquid
was drawn at a drawing rate of 24 mL/h for a drawing time of 30, 10
or 5 minutes. The drawing operation stopped after the above
predetermined drawing time. When permeation flux again reached
0.98.times.10.sup.-6 m.sup.3/(m.sup.2s), the drawing operation
started up again. The above operations were conducted repeatedly.
The results showed that when the drawing time was 5 minutes, the
concentration of .gamma.-globulin in the concentrated liquid
obtained was 22.5 g/L, i.e., 45.0 times as that in the feed; when
the drawing time was 10 and 30 minutes, the concentration of
.gamma.-globulin in the concentrated liquid obtained was 20.6 and
12.0 g/L, i.e., 41.2 and 24.0 times as that in the feed.
In view of the shortcomings existing in conventional membrane
concentration processes, such as severe membrane fouling, easy to
inactivate biomacromolecules, frequent cleaning of membrane and
difficult to operate continuously, the present invention provides a
continuous membrane separation method utilizing the characteristics
of concentration polarization layer such as rapid formation and
high solute concentration. This method comprises: adjusting the
thickness of a concentration polarization layer on membrane surface
and the concentration and distribution of solutes in the
concentration polarization layer by controlling the operation
conditions; and drawing the concentrated liquid in concentration
polarization layer by using a drawer for drawing the concentrated
liquid. When such method is employed, a desired solution with high
concentration can be obtained, the potential membrane fouling can
be significantly lessened, and a continuous concentration process
can be achieved. The method for concentrating biomacromolecules and
organic micromolecules utilizing concentration polarization
provided by the present invention skillfully solves the twinborn
problems of concentration polarization and membrane fouling during
membrane concentration process and reforms the principle and
implementation of membrane concentration techniques, and the
advantages of membrane techniques such as high efficacy, energy
saving, simple process and easy operation etc. are sufficiently
exhibited in the system of the present invention.
After reading the present invention, a person skilled in the art
can conceive many improvements and other embodiments of the present
invention and can predict the advantages thereof according to the
teachings of the present invention. Hence, it should be understood
that the embodiments and examples disclosed herein are not intended
to restrict the present invention, and the improvements and other
embodiments are also included in scope as claimed in the claims.
Although some specific terms are used in the text, they are used in
general and descriptive meanings, not intended to restrict the
scope of the claims.
* * * * *